package handlers

import (
	"html/template"
	"log"
	"net/http"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"task-dashboard/internal/api"
	"task-dashboard/internal/models"
	"task-dashboard/internal/store"
)

// isActionableList returns true if the list name indicates an actionable list
func isActionableList(name string) bool {
	lower := strings.ToLower(name)
	return strings.Contains(lower, "doing") ||
		strings.Contains(lower, "in progress") ||
		strings.Contains(lower, "to do") ||
		strings.Contains(lower, "todo") ||
		strings.Contains(lower, "tasks") ||
		strings.Contains(lower, "next") ||
		strings.Contains(lower, "today")
}

// atomUrgencyTier returns the urgency tier for sorting:
// 0: Overdue, 1: Today with time, 2: Today all-day, 3: Future, 4: No due date
func atomUrgencyTier(a models.Atom) int {
	if a.DueDate == nil {
		return 4 // No due date
	}
	if a.IsOverdue {
		return 0 // Overdue
	}
	if a.IsFuture {
		return 3 // Future
	}
	// Due today
	if a.HasSetTime {
		return 1 // Today with specific time
	}
	return 2 // Today all-day
}

// TabsHandler handles tab-specific rendering with Atom model
type TabsHandler struct {
	store                *store.Store
	googleCalendarClient api.GoogleCalendarAPI
	templates            *template.Template
}

// NewTabsHandler creates a new TabsHandler instance
func NewTabsHandler(store *store.Store, googleCalendarClient api.GoogleCalendarAPI, templateDir string) *TabsHandler {
	// Parse templates including partials
	tmpl, err := template.ParseGlob(filepath.Join(templateDir, "*.html"))
	if err != nil {
		log.Printf("Warning: failed to parse templates: %v", err)
	}

	// Also parse partials
	tmpl, err = tmpl.ParseGlob(filepath.Join(templateDir, "partials", "*.html"))
	if err != nil {
		log.Printf("Warning: failed to parse partial templates: %v", err)
	}

	return &TabsHandler{
		store:                store,
		googleCalendarClient: googleCalendarClient,
		templates:            tmpl,
	}
}

// HandleTasks renders the unified Tasks tab (Todoist + Trello cards with due dates)
func (h *TabsHandler) HandleTasks(w http.ResponseWriter, r *http.Request) {
	// Fetch Todoist tasks
	tasks, err := h.store.GetTasks()
	if err != nil {
		http.Error(w, "Failed to fetch tasks", http.StatusInternalServerError)
		log.Printf("Error fetching tasks: %v", err)
		return
	}

	// Fetch Trello boards
	boards, err := h.store.GetBoards()
	if err != nil {
		http.Error(w, "Failed to fetch boards", http.StatusInternalServerError)
		log.Printf("Error fetching boards: %v", err)
		return
	}

	// Convert to Atoms
	atoms := make([]models.Atom, 0)

	// Convert Todoist tasks
	for _, task := range tasks {
		if !task.Completed {
			atoms = append(atoms, models.TaskToAtom(task))
		}
	}

	// Convert Trello cards with due dates or in actionable lists
	for _, board := range boards {
		for _, card := range board.Cards {
			if card.DueDate != nil || isActionableList(card.ListName) {
				atoms = append(atoms, models.CardToAtom(card))
			}
		}
	}

	// Compute UI fields (IsOverdue, IsFuture, HasSetTime)
	for i := range atoms {
		atoms[i].ComputeUIFields()
	}

	// Sort atoms by urgency tiers:
	// 1. Overdue (before today)
	// 2. Today with specific time
	// 3. Today all-day (midnight)
	// 4. Future
	// 5. No due date
	// Within each tier: sort by due date/time, then by priority
	sort.SliceStable(atoms, func(i, j int) bool {
		// Compute urgency tier (lower = more urgent)
		tierI := atomUrgencyTier(atoms[i])
		tierJ := atomUrgencyTier(atoms[j])

		if tierI != tierJ {
			return tierI < tierJ
		}

		// Same tier: sort by due date/time if both have dates
		if atoms[i].DueDate != nil && atoms[j].DueDate != nil {
			if !atoms[i].DueDate.Equal(*atoms[j].DueDate) {
				return atoms[i].DueDate.Before(*atoms[j].DueDate)
			}
		}

		// Same due date/time (or both nil), sort by priority (descending)
		return atoms[i].Priority > atoms[j].Priority
	})

	// Partition atoms into current (overdue + today) and future
	var currentAtoms, futureAtoms []models.Atom
	for _, a := range atoms {
		if a.IsFuture {
			futureAtoms = append(futureAtoms, a)
		} else {
			currentAtoms = append(currentAtoms, a)
		}
	}

	// Render template
	data := struct {
		Atoms       []models.Atom // Current tasks (overdue + today)
		FutureAtoms []models.Atom // Future tasks (hidden by default)
		Boards      []models.Board
		Today       string
	}{
		Atoms:       currentAtoms,
		FutureAtoms: futureAtoms,
		Boards:      boards,
		Today:       time.Now().Format("2006-01-02"),
	}

	if err := h.templates.ExecuteTemplate(w, "tasks-tab", data); err != nil {
		http.Error(w, "Failed to render template", http.StatusInternalServerError)
		log.Printf("Error rendering tasks tab: %v", err)
	}
}

// ScheduledItem represents a scheduled event or task for the planning view
type ScheduledItem struct {
	Type        string    // "event" or "task"
	ID          string
	Title       string
	Description string
	Start       time.Time
	End         time.Time
	URL         string
	Source      string // "todoist", "trello", "calendar"
	SourceIcon  string
	Priority    int
}

// HandlePlanning renders the Planning tab with structured sections
func (h *TabsHandler) HandlePlanning(w http.ResponseWriter, r *http.Request) {
	now := time.Now()
	today := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
	tomorrow := today.AddDate(0, 0, 1)
	in3Days := today.AddDate(0, 0, 4) // End of 3rd day

	// Fetch Trello boards
	boards, err := h.store.GetBoards()
	if err != nil {
		log.Printf("Error fetching boards: %v", err)
		boards = []models.Board{}
	}

	// Fetch Todoist tasks
	tasks, err := h.store.GetTasks()
	if err != nil {
		log.Printf("Error fetching tasks: %v", err)
		tasks = []models.Task{}
	}

	// Fetch Google Calendar events
	var events []models.CalendarEvent
	if h.googleCalendarClient != nil {
		events, err = h.googleCalendarClient.GetUpcomingEvents(r.Context(), 20)
		if err != nil {
			log.Printf("Error fetching calendar events: %v", err)
		}
	}

	// Categorize into sections
	var scheduled []ScheduledItem   // Events and timed tasks for today
	var unscheduled []models.Atom   // Tasks due today without specific time
	var upcoming []ScheduledItem    // Events and tasks for next 3 days

	// Process calendar events
	for _, event := range events {
		item := ScheduledItem{
			Type:        "event",
			ID:          event.ID,
			Title:       event.Summary,
			Description: event.Description,
			Start:       event.Start,
			End:         event.End,
			URL:         event.HTMLLink,
			Source:      "calendar",
			SourceIcon:  "📅",
		}

		if event.Start.Before(tomorrow) {
			scheduled = append(scheduled, item)
		} else if event.Start.Before(in3Days) {
			upcoming = append(upcoming, item)
		}
	}

	// Process Todoist tasks
	for _, task := range tasks {
		if task.Completed || task.DueDate == nil {
			continue
		}
		dueDate := *task.DueDate

		// Check if task has a specific time (not midnight)
		hasTime := dueDate.Hour() != 0 || dueDate.Minute() != 0

		if dueDate.Before(tomorrow) {
			if hasTime {
				// Timed task for today -> scheduled
				scheduled = append(scheduled, ScheduledItem{
					Type:       "task",
					ID:         task.ID,
					Title:      task.Content,
					Start:      dueDate,
					URL:        task.URL,
					Source:     "todoist",
					SourceIcon: "✓",
					Priority:   task.Priority,
				})
			} else {
				// All-day task for today -> unscheduled
				atom := models.TaskToAtom(task)
				atom.ComputeUIFields()
				unscheduled = append(unscheduled, atom)
			}
		} else if dueDate.Before(in3Days) {
			upcoming = append(upcoming, ScheduledItem{
				Type:       "task",
				ID:         task.ID,
				Title:      task.Content,
				Start:      dueDate,
				URL:        task.URL,
				Source:     "todoist",
				SourceIcon: "✓",
				Priority:   task.Priority,
			})
		}
	}

	// Process Trello cards with due dates
	for _, board := range boards {
		for _, card := range board.Cards {
			if card.DueDate == nil {
				continue
			}
			dueDate := *card.DueDate
			hasTime := dueDate.Hour() != 0 || dueDate.Minute() != 0

			if dueDate.Before(tomorrow) {
				if hasTime {
					scheduled = append(scheduled, ScheduledItem{
						Type:       "task",
						ID:         card.ID,
						Title:      card.Name,
						Start:      dueDate,
						URL:        card.URL,
						Source:     "trello",
						SourceIcon: "📋",
					})
				} else {
					atom := models.CardToAtom(card)
					atom.ComputeUIFields()
					unscheduled = append(unscheduled, atom)
				}
			} else if dueDate.Before(in3Days) {
				upcoming = append(upcoming, ScheduledItem{
					Type:       "task",
					ID:         card.ID,
					Title:      card.Name,
					Start:      dueDate,
					URL:        card.URL,
					Source:     "trello",
					SourceIcon: "📋",
				})
			}
		}
	}

	// Sort scheduled by start time
	sort.Slice(scheduled, func(i, j int) bool {
		return scheduled[i].Start.Before(scheduled[j].Start)
	})

	// Sort unscheduled by priority (higher first)
	sort.Slice(unscheduled, func(i, j int) bool {
		return unscheduled[i].Priority > unscheduled[j].Priority
	})

	// Sort upcoming by date
	sort.Slice(upcoming, func(i, j int) bool {
		return upcoming[i].Start.Before(upcoming[j].Start)
	})

	data := struct {
		Scheduled   []ScheduledItem
		Unscheduled []models.Atom
		Upcoming    []ScheduledItem
		Boards      []models.Board
		Today       string
	}{
		Scheduled:   scheduled,
		Unscheduled: unscheduled,
		Upcoming:    upcoming,
		Boards:      boards,
		Today:       today.Format("2006-01-02"),
	}

	if err := h.templates.ExecuteTemplate(w, "planning-tab", data); err != nil {
		http.Error(w, "Failed to render template", http.StatusInternalServerError)
		log.Printf("Error rendering planning tab: %v", err)
	}
}

// HandleMeals renders the Meals tab (PlanToEat)
func (h *TabsHandler) HandleMeals(w http.ResponseWriter, r *http.Request) {
	// Fetch meals for next 7 days
	startDate := time.Now()
	endDate := startDate.AddDate(0, 0, 7)

	meals, err := h.store.GetMeals(startDate, endDate)
	if err != nil {
		http.Error(w, "Failed to fetch meals", http.StatusInternalServerError)
		log.Printf("Error fetching meals: %v", err)
		return
	}

	data := struct {
		Meals []models.Meal
	}{
		Meals: meals,
	}

	if err := h.templates.ExecuteTemplate(w, "meals-tab", data); err != nil {
		http.Error(w, "Failed to render template", http.StatusInternalServerError)
		log.Printf("Error rendering meals tab: %v", err)
	}
}